Conventionally, in case of analyzing an extremely small amount of polymers such as proteins and nucleic acids (DNA, RNA) contained in liquid, an electrophoresis apparatus has been used, and a liquid separation apparatus and a capillary electrophoresis apparatus are known as typical electrophoresis apparatuses.
A first conventional art for separating polymer components contained in liquid is a liquid separation apparatus and a liquid separation method that are disclosed in Japanese Publication for Unexamined Publication No. 281619/1999 (Tokukaihei 11-281619) (published on Oct. 15, 1999: corresponding to U.S. Pat. No. 6,132,597). The liquid separation apparatus is arranged so that a disk-shape substrate has a plurality of electrophoresis paths (flow paths) for electrophoresis, extending from a center of the disk in all directions, each of which has power source electrodes on its beginning point and termination. When liquid containing polymers are electrophoresed in each of the flow paths, the polymers are separated in terms of a molecular weight and an electrostatic property, and are electrically detected by a detection electrode provided in a vicinity of the termination of the flow path.
Further, a second conventional art for separating polymer components contained in liquid is a capillary electrophoresis apparatus disclosed in Japanese Publication for Unexamined Publication No. 304338/1997 (Tokukaihei 9-304338) (published on Nov. 28, 1997). This apparatus carries out not only the foregoing electrical detection but also fluorescence detection by binding fluorescent materials to polymers and emitting a laser beam or the like. The capillary electrophoresis chip (apparatus) is arranged so that: a position of a laser beam emission spot is fixed in a vicinity of the termination of the flow path, and a time taken for migrating polymers such as proteins and nucleic acids to pass the laser beam emission spot is detected, thereby detecting the polymers. This is based on the following reason: As a molecular weight of a polymer is smaller, the polymer passes faster, so that it is possible to specify a molecular weight and an electrostatic property on the basis of a time taken to pass the laser beam emission spot.
The first conventional art electrically detects polymers, and the second conventional art optically detects polymers. In this manner, they are different from each other, but they are identical with each other in that: a detection member is provided in a vicinity of the termination of the flow path, and the detection is carried out when the target polymer passes the detection section.
However, when target polymers are different from each other in terms of a molecular weight and an electrostatic property, some polymers are separated quickly and other polymers are separated slowly by electrophoresis. Despite of the difference, the detection section of the first and second conventional arts is fixed, so that the detection is not carried out until the polymer reaches the detection section even when the separation is completed quickly. Further, a polymer which is slowly separated reaches the detection section before the separation is completed, so that it is impossible to carry out the separation and detection.
That is, in the conventional sample detection apparatus, the detection member of the detection device is fixed, so that it is difficult to efficiently detect various polymers.
Further, the disk-type sample detection device of the first conventional art is characterized in that: its rotation enables sample liquid to be sequentially injected; it is possible to detect the separation in the flow path; and the like. However, in case of carrying out electrophoresis, it is necessary to supply power to the sample detection device (it is necessary to apply a voltage or to supply a current to the sample detection device), but the first conventional art has no recitation concerning the power supply.
Further, in case of optically detecting polymers by using the sample detection device of the second conventional art, an electrode and a wiring that are provided so as to supply power shield a light path of the light beam, so that it is impossible to efficiently carry out the optical detection for polymers.
Moreover, the first conventional art has the detection section in a vicinity of the termination of the flow path in order to electrically detect polymers, and the detection is completed when a target polymer passes the detection section. However, according to the electrical detection, an amount of a signal is small and an S/N ratio is low, so that it is difficult to sufficiently detect some kinds of polymers.
Then, there was proposed an apparatus which improves the detection sensitivity by raising the S/N ratio in accordance with not the electrical detection but the optical detection. This is the second conventional art. According to the apparatus, a laser beam is emitted onto a polymer migrating in the flow path, and light transmitted from the polymer is detected, so as to raise the S/N ratio, thereby optically detecting the polymer with high sensitivity.
However, the apparatus of the second conventional art is arranged so that: a light path of laser incident light is bent by a first reflection film at a right angle, and the light is transmitted through the polymer, and then the transmitted light is bent by a second reflection film at a right angle, thereby detecting reflected light of the transmitted light. Thus, a light path of incident light and a light path of reflected light of the transmitted light are not identical with each other, so that it is necessary to provide at least two optical systems such as object glasses for incident light and for reflected light. Therefore, a size of the apparatus itself is large.